By Helen Reid JOHANNESBURG (Reuters) – The United States and Britain are boycotting some Kimberley Process meetings because they are chaired by Russia, in a sign of how geopolitical rifts due to Russia’s invasion of Ukraine are affecting international diamond certification efforts. The Kimberley Process, set up in 2003, is an 85-nation body that certifies rough diamond exports and monitors members’ implementation of requirements aimed at stemming the flow of conflict diamonds. The division risks causing stagnation at the Kimberley Process, undermining efforts to ensure better controls against …